The Y chromosome: a graveyard for endogenous retroviruses.

We have isolated 20 different human endogenous retroviruses (ERV) related to ERV3, Hsrirt and Humer 4-1. Phylogeny and the presence of these ERV among different primates were determined by computer and Southern blot analyses. Preferential localization of ERV to the human, chimpanzee and orangutan Y chromosomes among the low-copy-number ERV is demonstrated. The reason for this accumulation of ERV on the strongly heterochromatic Y chromosome is probably mediated by (i) the absence of recombination of the Y chromosome that makes it more difficult for sequences to be lost, and (ii) integration of retroviruses in heterochromatic regions is less harmful to the organism. If ERV located on the Y chromosome are transcribed and translated to peptides, such peptides could be potential HY-antigens.